Method for cleaning oven walls



United States Patent 3,537,894 METHOD FOR CLEANING OVEN WALLS Ralph Brewster Thompson, Oak Brook, 11]., assignor to Nalco Chemical Company, Chicago, Ill., a corporation of Illinois No Drawing. Filed Oct. 8, 1968, Ser. No. 767,586

Int. Cl. C23g 5/00 US. Cl. 134-2 9 Claims ABSTRACT OF THE DISCLOSURE An oven wall cleaning composition having as the active cleaning agent a salt selected from the group consisting of sodium chlorate, sodium chlorite, sodium perchlorate, sodium nitrite and mixtures thereof, adapted to be spread over an oven wall surface that has become glazed with heat-produced fatty residues. Cleaning is effected by heating the treated surface to a sufiiciently high temperature, above about 230 C., for a period of time sufficient to burn off the fatty residues and leave the surface substantially clean. The cleaning composition can be applied dry to a lower horizontal surface or can be dispersed in a carrier, such as a gel, with or without a surfactant, and applied by brushing, spraying, wiping or rubbing onto the wall surface. A hydrocolloid gel is suitable for containing the selected salt in solution or dispersion.

SUMMARY OF THE INVENTION The method of my invention comprises applying a cleaning composition to a metal or other wall surface that has thereon a heat-produced glaze, film, stain or the like containing residues from fats, fatty oils and other fatty substances of vegetable or animal origin. The method of cleaning is especially applicable to cooking oven walls formed of aluminum or other metal, whether bare or coated, as with porcelain enamel. During use in cooking, such oven walls become spattered with grease from food, especially in the broiling, roasting or baking of meats, and in time the walls are coated over with a glaze of heat-produced residues of such grease. These residues adhere tightly to the interior oven walls to form an unsightly stained coating or film, herein generally referred to as a glaze.

In some of the more modern electrically heated ovens, the glaze can be burned off by raising the temperature of the oven walls sufiiciently high, in the neighborhood of 700 to 800 F., to burn off the glaze and leave the wall surfaces substantially clean and of their original color. The burn-off can be satisfactorily carried out without the previous application of any cleaning composition but a large amount of electricity is consumed in heating up the oven walls to such high temperatures.

The present method is carried out at substantially lower temperatures that range from a minimum of about 230 C. to not over about 260 to 290 C.

My cleaning composition contains as the active cleaning agent a salt selected from the group consisting of sodium chlorate, sodium chlorite, sodium perchlorate, sodium nitrite and mixtures thereof. While other salts and even caustics, such as sodium hydroxide, have been tried, no salts or combination of salts have been found so effective in cleaning as those salts just named, and none so free from deleterious attack upon the surface itself of the oven wall, particularly where the wall is made of aluminum.

The selected salt or mixture of salts can be applied in dry powdered or granular form or dispersed in a suitable vehicle that can be applied by spraying, brushing, wiping or rubbing onto the glaze-coated surface to be cleaned. After application of the active ingredients of my compo- 3,537,894 Patented Nov. 3, 1970 "ice sition in an amount equivalent to about 0.01 to about 0.05 grams per square centimeter of the surface to be cleaned, the surface is heated to a sufficiently high temperature and for a sufiicient length of time to burn off the glaze and leave a clean surface behind. The term burn-off is used in the same sense as it is applied to the results obtained when the walls of an electrically heated cooking oven are brought up to a temperature sufiiciently high to remove unwanted grease stains, coatings and the like. It has not been determined with certainty whether the cleaning results are due to actual burning oif, assisted by the oxidizing efi'ect of a salt such as sodium chlorate or perchlorate, or by decomposition of the salts, or are due merely to vaporizing or otherwise dissipating the coatings of grease residues. If any salts are left behind on the oven wall surface, they may be wiped or washed oif with the aid of water.

DETAILED DESCRIPTION OF THE INVENTION Of the many salts and other compositions tested for use in the cleaning of cooking ovens only sodium chlorate (NaClO sodium chlorite (NaClOg), sodium perchlorate (NaClO and sodium nitrite (NaNO have been found to be satisfactory when used alone or in admixture. Sodium chlorate and sodium nitrite are the preferred salts.

In the following table, data are given as to the effect of sodium chlorate and sodium nitrite under varying conditions of treatment as indicated by the column headings. The data are applicable to the cleaning of metal surfaces on which a glaze has been produced by heating a relatively saturated non-drying fat in the form of a film on a metal surface. Residues of unsaturated fat are generally more difiicult to remove than saturated fat. Specifically, in gathering the data given below, a metal surface was coated with a film of a 30% solution of lard in normal-butyl alcohol and baked for the indicated number of hours at about 287 C., or 550 F., to form a glaze, cooled and then heated to the designated temperatures and for the designated times to effect a burn-off.

TABLE NO. 1

Times, hours G./cm. of glaze Percent clean Treatment Baking 1 Burning off oooo opp 0000000000000 MHHOMHHOMMNMQ: awomwooomrooouofiocu As will be noted from the data given in Table No. 1, if from to clean is considered acceptable, this result can be obtained by the use of as little as 0.016 g./cm. of NaNO or of NaClO if either a 1 or 2% hour burn-off time is used and to clean can be obtained by the use of 0.020 of either NaNO or NaClO with a 2% hour burn-off time at a temperature of about 287 C. (550 F.)

At lower temperatures, such as 260 C. (500 F.) even with the same weight of NaClO or NaNO per square 3 centimeter, less satisfactory cleaning was obtained, as shown in the following table:

TABLE NO. 2

(Sh/em. Temperature of Percent Treatment of glaze burning ofi, clean At a temperature of 232 C. (450 F.) no burn-off was observed even when subjected to that temperature for 2% hours. Raising the temperature to 250 C. (482 F.) achieved only a slight burn-off, but a further increase of temperature to 260 C. (500 F.) gave the results shown in the following table:

TABLE NO. 3

Treatment Galem. of glaze Percent clean The minimum temperature for eifective cleaning is higher than 230 C. and at least about 250 C., depending upon the nature of the fat or fats from which the residues are produced, the temperatures at which they have been baked onto the oven walls and the thickness of the glaze. A temperature of about 287 C. is sufiiciently high for removing any of the heat-produced glazes usually encountered, so that while higher temperatures can be used their use is less economical.

While the data given are based upon the use of the preferred salts, sodium nitrite and sodium chlorate, any of the other salts named can be used by themselves of in admixture with one another with entirely comparable results. The values assigned to Percent Clean were obtained by visual observation and are believed to be reproducible within a possible variation of 5 to either way.

In applying the cleaning composition, the active salt ingredients can be spread over the surface either dry, if the surface is an upwardly facing horizontal surface, or in an aqueous vehicle in the form of a saturated solution, slurry, gel or the like, preferably with a surfactant to assist in spreading the aqueous dispersion over the glaze.

Application of the active ingredients dispersed in a hydrocolloid gel is preferred since the gel can be easily applied to all of the oven surfaces. By way of exemplification, a hydrocolloid gel can be prepared by stirring about 1% of a suitable gel-forming substance into water and then introducing the desired amount of the selected salt into the gel with vigorous agitation. Various gel-forming substances, such as fermented polysaccharides and the like, can be used in making a suitable hydrocolloid gel. The selected salt can be incorporated into the gel in any desired amount up to its saturation point. All of the salts named herein are relatively highly water soluble.

The following is a gel composition that is entirely satisfactory for use in the method o'f my invention:

One part by weight of a fermentation-degraded polysaccharide (designated as B-1459 by the United States Department of Agriculture, Peoria, Ill.) is mixed with 99 parts by weight of Water with vigorous agitation until a thick, viscous gel is obtained. Into 60 parts by weight of this gel are stirred about 40 parts by weight of sodium chlorate until completely dissolved therein. The resulting gel remains stable over long periods of time and can be applied to oven surfaces in any of the ways heretofore mentioned. Any surfactant, such as Aerosol OT, a dioctyl ester of sodium sulfosuccinic acid, in amounts from 0.1 to 1% by weight can be incorporated into the gel.

After the burn-off, if salts remain on the oven walls, they can be removed by wiping with a wet rag or sponge. If a clean surface is obtained, the oven wall will be restored to its original color.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention: 1. The method of cleaning a metal surface having thereon a heat-produced glaze of fat residues, which comprises spreading over said glaze a composition consisting essentially of a salt selected from the group consisting of sodium chlorate, sodium chlorite, sodium perchlorate, sodium nitrite, and mixtures thereof, and

heating said salt-spread glaze to sufiiciently high temperature above 230 C. for a sufficient length of time to remove said film and leave said surface substantially clean.

2. The method as defined by claim 1, wherein the metal surface is an aluminum surface, and

the salt-spread glaze is removed without any substantial attack on said aluminum surface.

3. The method as defined by claim 2, wherein the aluminum surface is the interior surface of a cooking oven, and

heating is accomplished by raising the temperature of the salt-spread glaze to at least 260 C. for at least about one hour.

4. The method as defined by claim 3, wherein at least about 0.01 gram/cm. of said salt composition is spread over said glaze.

5. The method as defined by claim 1, wherein the salt selected is spread over said glaze in an amount equal to at least 0.02 gram per square centimeter of said glaze, and

the salt-spread glaze is heated to a temperature of at least about 260 C. for at least about an hour.

6. The method as defined by claim 5, wherein said metal surface is the inner surface of an aluminum cooking oven.

7. The method as defined by claim 6, wherein said selected salt is dispersed in a hydrocolloid gel and the resulting composition is spread over said glaze by brushing.

8. The method as defined by claim 1, wherein said composition consists essentially of at least 40% by weight of the selected salt dispersed in a hydrocolloid gel.

9. The method of claim 8, wherein the heating is carried to about 260 C. and maintained at that temperature for at least about 2% hours.

References Cited UNITED STATES PATENTS 2,443,373 6/1948 Borsoif 13420 2,674,549 4/1954 Balz 134-2 3,085,035 4/1963 Ireland et al. 134-2 XR 3,375,155 3/1968 Adams 134-2 XR 3,423,568 1/1969 Meckley et al. 134-2 XR FOREIGN PATENTS 632,401 12/ 1961 Canada.

MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, Assistant Examiner US. Cl. X.R. 134-22, 39 

